Influence of Cysteinate Protonation on Biologically Relevant Nickel-Mediated Reactions

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In this project funded by the Chemical Structure, Dynamics and Mechanisms B Program of the Chemistry Division of the NSF, Professor Jason Shearer of the Department of Chemistry at University of Nevada, Reno is studying the influence of protonated sulfur ligands at the active sites of metalloenzymes. This type of structure has recently been recognized as important in several metalloprotein active sites, yet its impact on structure and catalysis has not been well studied. This project examines a number of well-defined synthetic nickel-sulfur compounds and evaluates their reactivity, structure and properties. The research has impacts on the design and production of a number of catalytic systems, including those important in clean energy, commodity chemical, and pharmaceuticals. In addition, the project provides an educational platform for the training of highly skilled workers in a number of Science, Technology, Education and Mathematics (STEM) fields.Cysteinate-ligated metalloenzymes represent a diverse class of biomolecules that are involved in reactions ranging from electron transfer to hydrocarbon functionalization. Recently, it was discovered that the active site of nickel-iron hydrogenase contains a protonated-coordinated nickel-sulfur bond. This adds to a small, but growing number of enzymatic systems, such as nickel superoxide dismutase that contain this structural element. This research group has recently shown that this feature is not only important in modulating the structure and properties of nickel-thiolate ligated systems, but can also be involved in reactions such as proton coupled electron transfer reactions. This research seeks to understand the properties and reactivities of designed nickel containing small molecules and metallopeptide-based systems that contain the protonated nickel-sulfur bond. A series of spectroscopic, computational, reactivity, and mechanistic studies are undertaken to understand these systems. Information learned through these studies is used to rationally design systems with fine-tuned electronic and geometric structural properties that can perform specific reactions towards targeted substrates.